There are a multitude of applications in industry where it is necessary to test a hollow fabricated body for fluid leakage. For example, the manufacture of blow plastic containers requires a rapid yet reliable leak tester to insure that the empty containers shipped to the bottler or packer are free from leaks.
A number of leak testers have heretofore been proposed and have primarily been based on a method involving the application of a fluid pressure to the container or object to be leak tested, measuring the flow rate or pressure drop to provide an indication of the existence of any leak, and converting the flow rate or pressure drop measurement into an electronic signal which is then applied to effect the energization of an "accept" or a "reject" light or signal and an appropriate counter. Typical of such prior art leak testers is that disclosed in U.S. Pat. No. 3,872,712 to Westervelt et al.
The testing unit disclosed in the Westervelt patent employes an excessive number of electronically actuated valves and relays to accomplish the required testing sequence. Moreover, the utilization of integrated circuits to effectively reduce the size and complexity of the described unit requires a supply of a significantly reduced, regulated voltage, free of noise and other electronic interference which are characteristic of a factory environment wherein the leak tester unit is most conveniently employed. There is, therefore, need for simplified leak testing apparatus and, in particular, a need to obtain the reliability and accuracy of integrated circuitry in a leak tester without resorting to actual utilization of such circuitry.